Jose Antonio Vargas detained in Texas

7/15/14 10:36 AM EDT

Former reporter and undocumented immigrant Jose Antonio Vargas was detained by Border Patrol agents as he tried to fly out of a Texas airport on Tuesday, the group United We Dream said in a statement.

Vargas tweeted a photo of his Philippine passport — which does not have a U.S. visa — and a copy of the Constitution before attempting to board a plane to Los Angeles at McAllen/Miller International Airport, writing that he didn't know what would happen. Define American, the organization Vargas founded to spread the word about undocumented immigrants, tweeted a photo of Vargas in handcuffs.

"Vargas originally traveled to the border in support [of] United We Dream (UWD) and Minority Affairs Council (MAC), a local UWD affiliate, in order to highlight the stories of refugee children who have fled countries in Central America because of increased levels of violence," United We Dream said in a statement. "The organizations have been volunteering in shelters that provide support to children and families."

Vargas, who won a Pulitzer Prize as part of a Washington Post team in 2008, has become an outspoken advocate for undocument immigrants after "coming out" as undocumented in a New York Times story in 2011. A CNN film directed by Vargas about his personal story as an undocumented immigrant aired in June on CNN.

In an essay for POLITICO Magazine on Friday, Vargas said he realized he'd have trouble getting out of Texas because of stricter immigration procedures.

Correction: An earlier version of this post misidentified the group Vargas founded. It is Define American, not United We Dream.